1. Field of the Invention
This invention relates generally to additive carriers for mixing with compositions such as mortar, grout, stucco and other materials, and more particularly to a viscous breakable gel additive carrier for mixing with ion containing materials which, in its gel form, prevents separation and settling of the additives prior to mixing and is easily measurable, and upon mixing with the ion containing materials liquefies and becomes totally and evenly miscible to allow easy and precise mixing to produce uniform homogeneous mortars, grouts, stuccos and other compositions.
2. Brief Description of the Prior Art
Mortars, grouts, stuccos, and similar materials have long been known. In Central America the Maya used pigmented stucco to decorate their temples and pyramids centuries ago. Most commonly, a dry powder consisting of Portland-type cements, fine silica, pigments and hardening agents mixed with water are used to produce these materials. Although the dry additives will not settle from the dry base materials, precise and even distribution in the finished product is difficult to achieve. Prior art methods of mixing "dry additive" materials on the job results in the loss of much time, labor, and material due to the difficulty of obtaining uniform distribution of the additives and/or pigmentation throughout the material to be used. On small jobs, it is common to waste of the majority of the dry ingredients because the remaining partial sack contents will hydrate and form lumps thereby becoming unusable when stored in containers that have been opened or broken open.
More recently, methods have been developed that utilize suspension enhancing agents to carry additives and pigments in water, and then the aqueous composition is added to the powdered dry base. Failure is often common even with these methods, because the additives have settled out of their liquid carriers in the storage containers. Also, often prior to use, workmen at the job site do not shake, stir, or properly mix the additives that have settled out of the liquid suspension. The resulting material may show shade differences due to uneven mixing of pigments because the first portion of the aqueous carrier taken from the top of the container's contents may contain little pigment and the pigment concentrations increase as the bottom of the source container is approached. Another problem that can occur with uneven mixing of the additives is that it can produce varying strength of materials. This problem may not be seen immediately but may soon result in a physical breakdown of the finished product.
Others have patented methods and compositions for use with mortars, grouts, stuccos, plasters, adhesives, and other products, and to overcome such problems as adhesion, installation qualities, freeze-thaw resistance, decreasing weight, acoustical qualities, texturing, multiple colors, etc. However, most workmanship claims in the industry are due to uneven coloring of applied cementitious mortar or other finish, which is usually caused by uneven distribution, and availability of the pigments prior to application. Additionally, workmanship claims are common because of the problem of mortar strength failure due to uneven mixing and distribution of other additives.
Making additives uniformly available when hydrating ion containing materials such as Portland-type cements and other calciferous products has long been a problem. It is well known that dry blenders build up static charges that can cause some polar additives to agglomerate and thereby lose their ability to attain uniform distribution. Some mineral pigments are particularly charge sensitive with resultant streaking of colors and severe shading causing job failure. The breakable gel additive carrier in accordance with the present invention overcomes charge sensitivity.
Some additives such as hydroxymethylcellulose and hydroxyethylcellulose, to name only two, absorb water needed for hydration, then release it slowly. This allows the materials compounded therewith to cure uniformly when used in conjunction with a substrate with high absorption capacity that would otherwise rapidly extract the water. If extreme care is not taken in the formulation process a cement matrix can suffer excessive retardation of "set" due to its inability to extract the water needed for hydration from the cellulose. It is vital to choose the correct type, viscosity, and amount of cellulose material. Failure can still occur unless it is distributed evenly in the end product. The breakable gel additive carrier in accordance with the present invention imparts homogeneous distribution.
Agents used for suspending additives serve no purpose other than to prevent the desired additives from separating out of the aqueous phase prior to mixing with ion containing materials such as cementitious powders. Because of the inefficiency of most such suspension agents, they must be used in significant quantities. Any material other than water, when added to dry cementitious materials will compromise the strength of the end product produced. Limiting the quantity of additives therefore is imperative unless the additives serve a useful purpose. Pigments, cellulose derivatives, latex, and similar materials have specific uses. Clays, starches, gums, protein, animal glues, and other materials have no purpose other than suspension agents and therefore should be avoided if possible. The breakable gel additive carrier in accordance with the present invention prevents the additives from separating prior to mixing with ion containing materials.
Water availability to the hydrating Portland-type cements is critical because it largely determines the ultimate strength of the "set" cement matrix. Portland-type cements will normally utilize up to 30% of their own dry powder weight in the hydrating process. Changes in water availability by additives whose sole function is to increase stability of the aqueous composition prior to addition to the cementitious base will compromise the coloration and strength of cement based compositions. Without competition from unnecessary suspension enhancing agents, cellulose derivatives are more efficiently hydrated and assimilated, therefore greatly decreasing the quantities required. Current methods require 0.5% to 10% suspension enhancing agents, whereas the breakable gel additive carrier in accordance with the present invention provides flawless additive carrying capacity with less than 0.02% suspension enhancing agents.
Colorant (pigment) addition to Portland-type cements utilizing aqueous carriers also presents specific problems. The cement to water ratio is important for proper hydration and to prevent shading from batch to batch. It is customary, and usually necessary, that more than one batch must be mixed by the end user to complete large areas. If, on the second and subsequent batches, the mixing water is increased or decreased by even small percentages, the entire job could be rejected. The breakable gel additive carrier in accordance with the present invention, without masking by unnecessary suspension enhancing agents, requires less pigment while still resulting in brighter and more saturated coloration of the composition.
Most chemical additives, especially pigments, will separate and sink to the bottom of the container, even when suspension enhancement agents are used. This makes them difficult or impossible to again evenly and homogeneously disperse and use especially in large containers. The breakable gel additive carrier in accordance with the present invention overcomes these and other problems in its ability to "pre-wet" or "pre-mix" the additives in the proper amount of water normally used in the hydration process.
There are several commercially available products and patents directed toward various compositions for mixing with ion containing materials such as dry powder based cementitious materials, mortars, grouts, stuccos, etc.
Dryvit Systems, Inc. of West Warwick, R.I., a division of RPM, Inc. of Medina, Ohio, one of the world's largest manufacturers of cementitious products for interior and exterior use, has been adding pigments and other additives to the aqueous portion of their products since the 1960s as part of their effort to solve the problems encountered with uneven mixing of additives. Their biggest problems continue to be streaking and shading of their applied finished products. This is directly related to the difficulty of obtaining an even mix even though they have been adding pigments and additives to the aqueous portion of their mix for many years. Dryvit now allows their end users to mix additives/pigments at the job site because they have found no method to keep them homogeneously suspended in their products if mixed at the factory.
Bowden, U.S. Pat. No. 4,204,876 discloses a method of using thixotrophic compositions to carry additives in the liquid portion of cementitious products as a method of attempting to gain homogeneity of the end product.
Johansen et al, U.S. Pat. No. 5,558,708 discloses a "two-component" system and method for dispensing pigment in cement based composition using a predetermined and prepackaged amount of an aqueous liquid pigment carrier component that is mixed with a predetermined and prepackaged amount of a powder cement component to obtain standardized colors. Although this system has merit it does not solve the problem of color and additive variance within batches because the pigments and additives commonly, and usually very rapidly, settle out of the liquid leaving a virtually clear liquid at the top and a concentration of additives and pigments at the bottom of the container. Vigorous stirring, shaking, or otherwise mixing of the pigment carrier component after storage and prior to combining with the powdered materials is required. Relatively large quantities of suspension enhancing agents are required that serve no other purpose. These agents mask, dilute, change, or otherwise compromise the final composition. Additionally, products with large quantities of suspending agents must be sold in small containers to facilitate shaking by the end user.
Johansen et al, U.S. Pat. No. 5,846,315 disclose a method for preparing a pigment dispersing pigment cement composition comprising water, pigment, a suspension enhancing agent and latex polymer solids. Two or more prepackaged compositions of an aqueous liquid pigment component is mixed with a prepackaged amount of a dry powder cement component to obtain cement composition with a uniform and standardized color. The suspension control agents, viscosity control agents, etc., two or more of which are required, are thoroughly mixed together prior to combining with the prepackaged dry powder cement. Agents that merely increase the viscosity of the aqueous component sufficient to carry the desired additives preclude its use in acting as a source of water in calciferous materials.
Johansen et al, U.S. Pat. No. 5,855,665 disclose a system and method for producing a pigmented cement compositions that uses significant percentages of only marginally effective suspension enhancing agents. Vigorous shaking, stirring, or otherwise mixing is still required which also limits container size to that which can be conveniently handled by workmen. Furthermore, the significant concentrations of suspension enhancing agents and dispersants required in the aqueous coloring composition can be deleterious to the makeup and strength of the end product. Additionally, the setting aids required are essential because the products also contain chemicals that compromise setting. These materials can also be detrimental to the ultimate strength of the final mix. This system also requires the mixing of additional water into the prepackaged pigmented cement compositions.
The present invention is distinguished over the prior art in general, and these patents in particular by a viscous breakable gel additive carrier for mixing with ion containing materials, including dry powder based and calciferous materials, which in its uniform homogeneous gel form, prevents separation and settling of the additives prior to mixing and is easily measurable, and upon mixing with the ion containing materials liquefies and becomes totally and evenly miscible to allow easy and precise mixing to produce uniform homogeneous mortars, grouts, stuccos and other compositions. The gel includes a predetermined amount of selected additives thoroughly mixed with a cross-linked polyacrylic acid gelling agent, an organic chelating agent, and an alkaline electrolyte, and prior to mixing with ion containing materials, has the consistency of a custard or jelly.